Propulsion systems for boats



' Sept 22, 1959 E. J. CLERK 2,905,133

PROPULSION SYSTEMS FOR BOATS Filed April 1, 1958 INVENTOR ERNEST JOSCELYN CLERK ATTOR/VE Y5 United States Patent PROPULSION SYSTEMS FOR BOATS Ernest Joscelyn Clerk, Jamaica, British West Indies Application April 1, 1958, Serial No. 725,543

3 Claims. (Cl. 115-41) This invention relates to propulsion systems for boats in which an engine mounted inboard of the boat drives a screw propeller so mounted on a support that the axis of the propeller is movable relative to the fore-and-aft axis of the boat for steering, the support itself being pivotable about a horizontal axis to lift the screw propeller clear of the water.

According to the invention, in a propulsion system for a boat including a screw propeller adapted to be driven by an engine mounted inboard of a boat and so mounted on a support that the axis of the propeller is movable relative to the fore-and-aft axis of the boat for steering, the support itself bein pivotable about a horizontal axis to lift the screw propeller clear of the water, the screw propeller support includes a forwardly extending arm in which is rotatably mounted a shaft connected by gearing to the propeller shaft, the said shaft having at its forward end a sprocket wheel cooperating with the upper end of a sprocket chain loop engaging at its lower end with a sprocket driven by the engine, the screw propeller support being mounted on a horizontal pivot so positioned that upward swinging movement of the screw propeller about the said pivot is accompanied by downward swinging of the forward end of the arm to disengage the sprocket thereon from the chain, movable idlers being provided to support the chain when the said sprocket is disengaged therefrom.

The idlers are preferably mounted on spring-loaded arms so arranged that the idlers tend to move outwardly and widen the chain loop adjacent its upper end, thus allowing the upper end of the chain loop to move downwardly without the chain falling away from the driving sprocket.

The chain sprockets and idlers are preferably mounted in a chain case, and the screw propeller support may be pivotally mounted on a bracket adapted for attachment to the transom of a boat, the chain case being rigidly supported from said bracket.

The invention is hereinafter described with reference to the accompanying drawings in which:

Figure 1 is a sectional elevation of a propulsion system accordin to the invention which is shown mounted on the transom of a boat, the engine being omitted;

Figure 2 is a view of the sprocket chain mechanism lookin from the rear; and

Figure 3 is a view looking from the rear of the bracket on which the system is mounted and the chain case, the rear portion of the propeller support being omitted, and the position of the top of the boat transom when the bracket is secured thereto being shown in chain dotted lines.

Referring to the drawings, the rear portion of the boat is indicated at 10, the transom being shown at 11. A bracket 12 fitting over the upper edge of the transom and clamped thereto by a screw 13 is provided with two laterally spaced upstanding ears 14 between which extends, in a fore-and-aft direction, one arm 15 of an L-shaped member the other arm 16 of which extends downwardly outside the transom of the boat. The arm 15 of the L-shaped member 15, 16 is provided with two laterally extending trunnions 17 which extend between part cylindrical grooves in the upper ends of the ear 14 and corresponding grooves in bearing caps 18 mounted on the tops of the said cars, so that the L-shaped member is pivotable about a transverse horizontal axis with respect to the bracket 12. The arm 16 of the L-shaped member is extended downwardly by means of a rotatable pillar 19, the said arm 16 having a coaxial spigot 21 on its lower end which enters a recess 22 in the upper end of the pillar 19 to provide a bearing for the said pillar. Extending vertically through the arm 16 and the post 19 is a vertical shaft 23 carrying on its lower end one of a pair of bevel gears 24 the other of which is mounted on a propeller shaft 25 carrying a screw propeller 26. A bevel wheel 27 on the upper end of the shaft 23 meshes with a bevel wheel 28 on a shaft 29 extending forwardly through the arm 15 of the L-shaped member. The bevel wheels 27, 28 are housed in a cavity at the elbow of the L-shaped member 15, 16, this cavity being closed at its upper end by a cover 31 having an upstanding central boss 32 which engages in a cylindrical recess 33 in the underside of a tiller member 34 secured to the upper end of an offset arm 35 projecting upwardly from the pillar 19 alongside the arm 16 of the L-shaped member.

A chain case 36 is mounted inside the boat adjacent the transom 11 and is rigidly connected to the bracket 12 by means of bracing members 37, 38, 39. The bracing members 37 are attached to a common point 41 at the lower end of the chain case 36 and extend upwardly to laterally spaced points 42 at the lower end of the bracket 12. The bracing members 38 are secured at their lower ends one to each side of the bracket 12, and extend outwardly and upwardly to anchorage points 43 at the sides of the chain case 36, whilst the bracing members 39 extend upwardly and inwardly from the points 43 to further attachment points on the cars 14.

An engine (not shown) is mounted inside the boat and its driven shaft or another shaft directly connected thereto extends in a fore-and-aft direction into the lower part of the chain case 36 to carry a chain sprocket 44. The shaft 29 which extends forwardly through the arm 15 of the L-shaped member carries another chain sprocket 45, this sprocket 45, when the L-shaped member is in the position shown in Figure 1, lying, within the chain case in the same plane as the sprocket 44, and being adjacent with the upper end of the said chain case. A sprocket chain 46 runs over the two sprockets. Two arms 47, pivotally mounted in the chain case and extending downwardly from their pivotal mountings carry at their free ends sprockets 48 (or pulleys) which engage the chain 46 inside the loop thereof between the sprockets 44 and 45, the arms 47 being acted on by springs 49 which tend to urge them upwardly and outwardly. The upward and outward movement of the arms 47 is limited by stops 50 so as to ensure that they move through equal distances.

It will be apparent that the propeller 26 can be lifted out of the water by rocking the L-shaped member 15, 16 rearwardly and upwardly about the trunnions 17 and said rocking movement will cause the sprocket 45 to swing downwardly and rearwardly. The upper part of the chain loop will, of course, tend to move downwardly with the sprocket 45 introducing slack in the chain 46 which will be taken up by upward movement of the idler sprockets 48. Ultimately, when the upper part of the chain 46 extends in a substantially straight line between the sprockets 48, as indicated in dotted lines in Figure 2, the sprocket 45 will move away from the chain and the driving connection between the engine and the propeller will be broken. There will, of course, be some slight movement in a fore-and-aft direction of the upper point on the sprocket 45 as the latter moves downwardly, but the axis of the trunnions 17 being in the same horizontal plane as the axis of the shaft 29, as shown in the drawings, and the chain being arranged to extend horizontally between the sprockets 48 when the said point on the sprocket 45 is moved downwardly through a distance equal to its diameter, the said point will be in the same transverse vertical plane when it disengages the chain as it is when the shaft 29 is horizontal. Consequently, on moving upwardly to engage the chain, the sprocket will be in the correct plane to engage it and there will be no danger of improper engagement. If preferred, the trunnion axis may be arranged above or below the axis of the shaft 29, thus reducing or increasing the angle through which the shaft 29 moves be-..

tween the two positions in which the upper point on the sprocket 45 is in the same transverse vertical plane. The idler sprockets 48 are then positioned to support the chain at a suitable level to be engaged with and disengaged from the sprocket 45 at the lower of these positions.

The rear face of the chain case is 'apertured to allow the inward and outward movement of the sprocket 45, but otherwise forms a complete enclosure for the sprocket and gearing.

The part of the bracket 12 which lies outside the transom is provided with an abutment 51 adapted to be engaged by the arm 16 of the L-shaped member to transmit the thrust of the propeller to the boat.

If desired a separate thrust abutment may be provided, directly mounted on the transom, particularly if the engine is a powerful one.

The driving sprocket 44 may be mounted on a shaft which is coupled to the engine shaft by a universal joint so that the position of the engine can be determined independently of the drive mechanism, any misalignment between the engine crankshaft and the axis of the sprocket 44 being taken up by the universal joint.

I claim:

1. A boat propulsion system for driving a screw propeller h'om an engine mounted inboard of the boat, said system comprising a support pivotally mounted on a horizontal axis, an arm extending forwardly from said support, a first shaft rotatably mounted in said arm, a sprocket wheel on the forward end of said first shaft, a sprocket chain loop having its upper end drivingly connected to said sprocket wheel and its lower end drivingly connected to the inboard engine, a pillar pivotally mounted on said support, a propeller shaft having a screw propeller thereon and rotatably mounted in said pivotable pillar whereby the axis of the propeller is movable relative to the fore-and-aft axis of the boat for steering, means within said support and pillar for drivingly connecting the rearward end of said first shaft and said propeller shaft, the pivotal mounting of said support being so positioned that upward swinging of the propeller shaft about said pivotal mounting will lift the propeller clear of the water and is accompanied by a downward swinging of the forward end of said arm to disengage the said sprocket from said sprocket chain loop, and idlers movably mounted to support said chain loop when said sprocket is disengaged therefrom.

2. A boat propulsion system as claimed in claim 1 and further comprising spring-loaded arms for mounting said idlers with said arms being urged outwardly to widen the chain loop adjacent its upper end thereby enabling the upper end of the chain loop to move downwardly so that the lower end of the chain will remain drivingly connected with said engine.

3. A boat propulsion system as claimed in claim 2 and further comprising a bracket for attachment to the transom of the boat, said support being pivotally mounted on said bracket, and a chain case enclosing said chain sprocket and idlers rigidly supported from said bracket.

References Cited in the file of this patent UNITED STATES PATENTS 317,582 Schulze-Berge May 12, 1885 2,185,079 Hall Dec. 26, 1939 2,345,689 Snadecki Apr. 4, 1944 FOREIGN PATENTS 349,613 Great Britain June 1, 1931 

